The present invention relates to an improved method for the polymerization of chloroprene to produce polychloroprene having improved tensile strength. More particularly, the present invention relates to the discovery of new emulsifiers which produce unexpected improvements in tensile strength.
Any study of the prior art of polychloroprene, neoprene, will reveal an almost total disregard for the effect of the emulsification system on the resulting polymer. In general, most of the prior art has regarded the emulsifiers as roughly equivalent, in effect, with the primary consideration being directed to the satisfactory performance of the emulsificaton, e.g., the colloidal stability of emulsion.
It is taught in U.S. Pat. No. 3,392,134 to Apotheker, that the fatty acids such as straight-chain saturated or unsaturated carboxylic acids containing 12 to 30 carbon atoms or the dimers and trimers of unsaturated fatty acids are critical if the latex resulting during chloroprene polymerization is to be colloidally stable during post treatment.
It has now been found that the selection of a particular class of soluble salts of fatty acids as emulsifiers for the emulsion polymerization of chloroprene produces polymers having higher tensile strengths than the usual emulsifiers. Thus, it is a feature of the present invention that the same degree of emulsification efficiency may be obtained with higher tensile strength than achieved by the prior art.